1. Field of the Invention
The present invention relates to a louver fin type heat exchanger, and particularly, to a louver fin type heat exchanger having high reliability and improved efficiency by securely obtaining the air passageway in the heat exchanger, by minimizing a pressure drop of the air flow, and by controlling congregating of water drops formed by condensation (i.e., water blockage) at lower end portions of air passages of the louver fin type heat exchanger positioned upright at a certain angle with respect to the ground.
2. Description of the Background Art
In general, heat exchange between fluids is essential in a number of processes of heat-related industry. Therefore, various types of heat exchangers having improved efficiency in a heating system through effective heat exchange are being used. Of the heat exchangers, a heat exchanger used for a home air conditioner, an engine coolant system of a car, an air conditioning system of a car or the like, has fins securing a wider heat transfer area in order for the heat exchange with the external air.
Recently, the use of a compact heat exchanger having fins having a heat transfer area of about 100 m2/m3 or more is started according to demands for a leaner and lighter heat exchanger. The compact heat exchanger is divided into a plate-fin heat exchanger and a fin-tube heat exchanger. As the compact heat exchanger used in an air conditioning system, the fin-tube type heat exchanger was generally used. However, because the fin-tube type heat exchanger is problematic in that its weight is increased due to a copper pipe provide thereto and recycling of a material is difficult because materials of a fin and a tube are different, the fin-tube type heat exchanger is being replaced with the plate-fin type heat exchanger in the field of a package air conditioner and an air conditioning system for a car, which require to be leaner and lighter.
As shown in FIG. 1 to 3, a louver fin type heat exchanger 1, which is one of plate-fin type heat exchangers whose usable range is gradually increasing, includes two or more plates 10 and 20 formed of a metallic material and spaced apart from each other at a predetermined interval, a louver fin unit 30 coupled with the plates 10 and 20 and having at least one louver fin, and an air passage 40 formed between the plates 10 and 20 and the louver fin unit 30 for the purpose of allowing heat exchange between external air and the louver fin 30 or the like.
As shown in FIGS. 2 and 3, the louver fin 30 includes a plurality of louvers 31a bent at a predetermined angle to induce an air flow, and a plurality of through holes 31 between the louvers 31a to communicate with the air passages 40, thereby contributing to effective heat exchange between the air introduced from the outside and the louver fin 30.
Although FIG. 1 shows the louver fin type heat exchanger 1 in which one louver fin unit 30 is coupled between two plates 10 and 20, substantially, the plate-fin type heat exchanger to which the louver fin unit 30 is applied is constructed such that louver fins 30 are respectively bonded between a few plates 10, 20 or between several tens of plates 10, 20.
By such a construction, the air introduced from the outside in a first air-flow direction or a second air-flow direction passes between the plates 10, 20 and the louver fin unit 30, exchanging heat with the plates 10 and 20 and the louver fin unit 30. In such a manner, the heat of the plates 10 and 20 and the louver fin 30 is released to the outside or introduced thereinto.
However, if the louver fin type heat exchanger 1 (not shown) is positioned upright at a predetermined angle with respect to the ground and is simultaneously used as a freezer evaporator or the like, the air introduced into the heat exchanger is condensed while passing through the cool air passages 40 and moisture 90 flows down toward the ground by gravity. Thus, as shown in FIG. 4, moisture 99 irregularly congregates (i.e., water blockage occurs) on lower end portions of the louver fin unit 30 close to the ground. Here, because the moisture congregating on the lower end portions of the louver fin 30 blocks the air passage 40, the introduction to the air passage 40 or outflow of the air from the air passage 40 is not smoothly made, which causes an increase in a pressure drop of the air passing through the heat exchanger 1 and accordingly deteriorates heat exchange efficiency of the heat exchanger 1.
Furthermore, even though the heat exchanger is not used for the freezer evaporator in which the external air should pass through the cool air passage, the aforementioned problem may occur even when the louver fin type heat exchanger positioned upright at a predetermined angle with respect to the ground is used for a freezer condenser, a radiator, an oil cooler or the like and evaporation water is sprayed or dropped to improve cooling performance by an evaporation cooling effect. For this reason, a need to solve such problems is increasing.
In order to solve such problems, there was an attempt to reduce congregating moisture (i.e., water blockage) by reducing a contact angle between water and a fin by hydrophilic surface coating on a surface of the fin. Thus, as shown in FIG. 5, the extent to which the moisture congregates at the lower end portions of the louver fin 30 can be reduced as compared to the case where the hydrophilic surface coating is not performed. However, when a gap between the plates is 5 mm or less, the water blockage still occurs.
Particularly, from the view on the tendency that the gap is getting smaller in response to the demand for a smaller heat exchange, it can be known through the experiment of FIG. 5 that there is a limit in improving performance of the louver fin type heat exchanger only by hydrophilic coating.
As another solution for the congregating moisture of the louver fin type heat exchanger, research is conducted on reducing a contact angle between a fin and moisture by fabricating a porous fin with fine metal powder. However, this method is also problematic in that the moisture still congregates when pitches between fins are 5 mm or less.